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Current Regulatory Limit: Pentachlorophenol

Current Massachusetts Regulatory LimitMMCL = 0.001 mg/L. ORS has adopted the MCL published by the U.S. EPA (50 FR 46936; 56 FR 3526).

Federal Regulatory LimitThe MCL for pentachlorophenol is set at the PQL of 0.001 mg/L. The MCLG is equal to zero.

Basis for CriteriaAn MCLG of zero has been established for pentachlorophenol based on its designation as a B2 carcinogen. The MCL is based on the pentachlorophenol PQL.

Critical EffectsThe U.S. EPA currently classifies pentachlorophenol as a class B2 carcinogen. The MCLGs for B2 carcinogens are set at zero and the MCL is set as close to the MCLG as is feasible or at the 1 x 10-6 excess lifetime cancer risk. For pentachlorophenol, the PQL is the limiting factor and thus the MCL is set at the PQL of 0.001 mg/L.

Cancer Assessment: The cancer classification is based on limited evidence of increased incidence of biologically significant tumor types (hepatocellular adenomas, and carcinomas, adrenal medulla pheochromocytomas and malignant pheochromocytomas, hemangiosarcomas and hemangiomas) in mice. There was also a high incidence of two unusual tumor types, hemangiomas/hemangiosarcomas and adrenal medulla pheochromocytomas. There are mutagenicity data to support the cancer classification.

The MCL of 0.001 mg/L is associated with an individual excess lifetime cancer risk* of 3.3 in one million (56 FR 3526).

* This information on risk is extrapolated from information provided in the July 17, 1992 Federal Register that a 1 x 10-4 Excess Lifetime Cancer Risk (ELCR) is associated with a concentration of 0.03 mg/L.

PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at US EPA Drinking Water Analytical Methods
.

Other Regulatory DataAny Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:

Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at US EPA Current Drinking Water Health Advisories
.

RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at http://www.epa.gov/iris/. Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.